Electron tube



Nov. 22, 1938. A. A. THOMAS 2,137,424

ELEGTRON TUBE Filed 0G13. 20, 1936 INVENTOR:

Patented Nov. 22, 1938 UNITED STATES ELECTRON TUBE Adolph A. Thomas,

New York, N. Y., assignor to Radio Corporation of America, New York, N. Y., a corporation of Delaware Application October 20, 1936, Serial No. 106,503

13 Claims.

My invention relates to electron discharge devices and its object is to produce an all-metal tube embodying certain features of novelty whereby the manufacturing cost is lowered and the useful life of the tube prolonged as compared with prior devices of that kind. This metal tube is particularly adapted for use in radio apparatus, but my invention is not limited to that field.

One characteristic feature of my all-metal tube is a glass seal between the metal shell and the metal base disk of the envelope, whereby a perfect gas-tight weld is obtained between the metal parts. In prior radio tubes of this type, the metal shell and metal base are directly welded together, but this welding operation requires the most careful handling and it is diilicult to obtain a weld free from burning and one in which the metal parts are in complete contact uniformly all around. In the use of those prior metal tubes there have been complaints of leakage at the weld. This drawback is eliminated in my tube by uniting the metal shell and metal base disk into an integral gas-tight envelope by a sealing ring of glass, which is easily fused in place and produces a strong weld certain to be leak-proof in every instance.

Another novel feature of my invention resides the insulating mounting of the lead-in wires in the metal base of the envelope. In prior metal Ytubes the metal base disk has a number of holes (one for each wire) and around each hole is welded an alloy eyelet to which a small glass cylinder is fused, each cylinder carrying a lead- :in wire. In my tube I dispense with those separate sealing eyelets by forming the sheet metal hase of the envelope with integral cup-shaped projections which are filled each with a glass seal, and the lead-ln wires pass through these glass seals in such length of contact as to be rigidly supported.

The foregoing and other novel features and practical advantages of my invention will be understood from a description of the accompanying drawing, in which- Fig. 1 is a vertical section of an all-metal electron tube embodying my invention;

Figs. 2 and 3 are sections on lines 2--2 and 3-3 of Fig. 1;

Fig. 4 is a bottom view of Fig. 1;

Fig. 5 illustrates the position of certain parts during the sealing operation; and

Fig. 6 is a fragmentary section of a modification.

The evacuated envelope of the tube consists (Cl. Z50-27.5)

of a cylindrical metal shell or cup I0 and a metal disk I2, these two parts being integrally united in a vacuum-tight Joint by a sealing ring I3 of glass. The sheet metal parts III and I2 may be of steel, nickel, aluminum, duralumin, 5

, alloys of iron and nickel, and other metals found suitable for the purpose. To obtain a strong seal over 'a sufficiently wide contact area, I provide the metal shell I0 with an integral flange I4 and the metal disk I2 with an integral flange I5, 10 these flanges being spaced to form an annular recess I6 which is filled by the fused glass of ring I3.

Fig. 5 illustrates a simple way of fusing the glass sealing ring I3 in place: The shell I0 is held upside down on a suitable support (not shown) and the disk I2 is placed over the shell, the edge of the disk resting on shoulder I1 of the shell. Then the glass ring I3 (cut from a long tube) is placed in the recess I6, and is progressively heated, together with flanges I4-I5, by gas jets I8 properly arranged, until the glass melts and lls the recess I6, whereby the fused glass and the adjacent hot metal surfaces become welded together in a permanent gas-tight seal. As in all glass sealing operations, the assembled parts I0 and I2 are slowly rotated to insure uniform heating of the glass and the adjacent metal to the proper temperature.

The cross-sectional shape of the annular sealing space IB is preferably different from the normal rectangular cross-section of the glass ring I3 so as to provide a seal that also locks the parts together in a mechanical way. Thus, by forming opposite beads I9 and 20 on flanges I4 and I5, I provide an enlargement in the annular recess I6. When that enlargement is filled with glass from ring I3, the resultant seal positively locks the shell I0 and disk I2 against axial displacement aside from the adhesion of the glass to the metal. The cross-sectional area of ring I3 is so chosen with respect to the volume of recess IB that the fused glass fills the recess practically to the limit.

Attention is called to the depth or axial length of the glass seal I3 as determined by the length of flanges I4I5. This wide contacrl between the glass and the metal assures not only a vacuumtight seal but one that is mechanically strong to withstand even rough and careless handling 50 of the tube. It is not necessary that the contact between the edge of disk I2 and the shoulder I1 of shell I0 be a perfect fit, for thel fused glass I3 seals up any irregularities in that contact. No special skill or care'is required to make the 55y v cient el? expansion as 'the uum-tight union dormir perfect for all tubes. Exi tc insert the glass rings Il, be done by automatic machinery. surfaces in contact with the glass n. should have practically the same coeiliglass, so that the vacbetween the glass and metal parts is not aected by changes of temperature.

Either the metal itself of which the shell I0 and the disk i2' are composed has the same expansion coecent as the glass seal, or the glass-contacting surfaces of flanges I4-I5 are lined with such a metal. For example, the seal I 3 may consist of a borcsilicate glass (such as Pyrex) having a coefficient of expansion less than0.000004, and the sheet metal partsv I Il and I2 may be of an ironnickei alloy with substantially the same expansion coefficient. A commercially known alloy of approximately 63% iron and 37% nickel (called Invar) has an expansion coeillcient so low as to be practically negligible, and this alloy (or one like it) may be used for making the shell I0 and disk I2. Ordinarily these two parts will be made of sheet steel, which is cheap and strong, and is furthermore magnetic, so that the steel envelope also acts as an electromagnetic shield for the electrodes inside.

The sheet metald disk I 2 is formed with integral nipples 2| which provide cup-shaped recesses or craters filled with sealing glass 22. These nipples may extend either up or down from the disk and are preferably conical or convergent toward the outer end so as to hold the glass seals 22 more easily in position during the sealing operation. That is to say, the restricted end openings of nipples 2I keep the plastic glass of seals 22 from dropping out. The glass seals 22 support the lead-in wires or rods 2l in a strong vacuumtight joint and at the same time insulate them from the metal of disk I2. As seen in Fig. 1, the -axial depth of the glass seals 22 provides wide contacts thereof with disk I2 and wires 23, so that the latter are rigidly sealed in the disk and safely insulated. The coemcient of expansion of the glass in seals 22 should be practically the same as that of the lead-in wires 23 and the inner surface of nipples 2i, as previously explained for seal I2 and the metal parts I4-I5.

A suitable electrode assembly 24 is supported in the tube either directly on the lead-in wires 22 or independently thereof by separate members, according to well known practice. I have not considered it necessary to show or describe the structural details of the electrode assembly 24, since any practical arrangement and construction of electrodes may be used, depending upon the intended function of the tube. Thus, for radio reception the electrodes in the tube would be a cathode. an anode, and one or more control grids. It will therefore be understood that the dotted outline 24 in Fig. 1 represents any suitable construction and arrangement of electrodes.

A base disk 25 of molded insulating material (such as glass, porcelain, or a condensation product) is attached to the metal shell I0 by means of a sheet metal collar 25, which has an inturned top rim 21 engaging an annular shoulder 24 on the shell. The bottom edge of collar 24 has portions 29 indented into bevelled notches 20 in base 25, whereby the latter is firmly held within the collar against the annular glass-metal rim formed by the adjacent ends of parts I2I4I5. To mount the insulating base 25 on the tube, the

'metal collar 24 is slipped over the shell Il (or the latter is dropped inverted through the collar) until the rim 21 engages the shoulder'v 2l. 'I'he base disk 25 is then placed within the collar against the bottom edge of the sealed members portions 29 of collar 2B are peened into the notches 30 of disk 25. The bevelled surfaces of these notches cause the disk 25 and the rim 21 of collar 25 to be drawn together by the peening operation, so `that both the disk and the collar are held tightly in place. This method of attaching the base 25 to the tube isv very simple and dispenses with the, use of cement. The rim 21 may be soldered or otherwise attached to shoulder 28.

Before the base disk 25 it receives the contact pins 3i, of which four are shown by way of example, but the number of pins will depend upon the number of elements in the electrode assembly 24. pins 3i pass through holes in the disk 25 and are secured thereto by top tabs 32 and intermediate beads 3l formed integral on the pins. 'Ihese pins are hollow or tubular and the beads 23 are readily formed by radially expanding the tubular wall of the pin, so that the beads are integral hollow enlargements of pins 3|, which are made of suitable conducting metal. The tabs 32 (I have shown four on each pin for example) are bent out nat over the top of disk 25, which may have square or angular recesses 34 to Yreceive the tabs and prevent turning of the pins, although this detail is not essential. The beads 33 llt tight in recesses 35 on the underside of disk 25 and limit the inward axial movement of pins 3i. First, these pins are pushed through the holes in disk 25 as far as the beads 33 will let them go, then the tabs 32 are bent over in pressure contact with the top surface of the disk. .In this way the contact pins 3I are rigidly clamped to the base disk 25 without the aid of an adhesive, the disk being sufficiently thick to hold the pins steady.

The contact pins 2i are preferably hollow to receive the lead-in wires 23 in good electrical connection. A hole I4 in the center of disk 25 receives the exhaust tubulation 21 (which may be metal) depending from the disk I2, to which the tubulation is welded over the exhaust hole 28 of the disk. A lug 29 (integral or separately attached) on the bottom of disk 25 is so positioned as to enter a slot on the socket of the tube to assure the proper mounting of the latter for operation. 'I'he lug or pin 29 extends axially from disk 25 and may be of any suitable shape, it being shown rectangular in cross-section in the bottom view of Fig. 4.

In Fig. 6 the shell III and disk I2 (both of sheet metal) are integrally united by a glass sealing ring I I" which lls the annular recess between the flange 40 of shell I0 and the flange 4I of disk I2. The edge of this disk abuts against the shoulder 42 of shell III and this engagement definitely determines the width of the sealing space between the flanges 44-4I. 'Ihe normal thickness of the glass ring I3' is preferably somewhat greater than the axial depth of the recess between flanges 40-4I, so that the plastic mass of the ring is pressed against said flanges in complete vacuum-tight contact therewith when the flange 4I strikes the shoulder 42 during the sealing operation. Any excess of the plastic glass is squeezed out of the annular sealing space, as indicated at 42. A base 44 of molded insulating material Is held rigidly against the underside of flange 4I by the rim 45 of 1s attached to the tube,

The metal contact vvshell I6', this rim having portions 46 peened into slots 41 of the base. Otherwise, what has `been said about the materials and the expansion coefllcients of parts I0, i2 and il in Figs. 1-5 applies fully to the corresponding parts i0'|2'l3 in Fig. 6. It is also to be assumed that the disk l2', like disk l2, carries the necessary lead-in wires, and that the base member curacy required in shop drawings, and I have purposely exaggerated the relative dimensions of the parts for clearness.

Although I have shown and described certain specific constructions, I want it understood that my invention is not limited to the detalls set forth, for various changes and modifications may be resorted to without departing from the invention as defined in the appended claims.

I claim as my invention:

1. An.r electron tube having a gas-tight envelope consisting of a metal shell and a metal disk integrally united by a glass seal, said metal shell and disc having integral portions in abutting contact with each other along a circular line at one edge of said glass seal, and an electrode assembly in said envelope.

2. An electron tube comprising a metal shell provided with a flange, a metal disk also having a flange, said flanges being spaced to form an annular recess, said metal shell having an integral shoulder at one end of said recess, one end of the flange on said disc abutting against said shoul der, a sealing ring of glass filling said recess and fused to said flanges, whereby said shell and disk constitute a gas-tight metal envelope, and an electrode assembly in said envelope.

3. An electron tube having a gas-tight envelope consisting of a metal shell and a metal disk integrally united by a glass seal, cooperating means on the united glass and metal surfaces for mechanically locking the shell and disk together against axial displacement, said locking means being in addition to the adhesion of the united surfaces, and an electrode assembly in said envelope.

4. An electron tube comprising a sheet metal shell which terminates in an integral shoulder and a cylindrical flange, a sheet metal disk terminating in a cylindrical flange, said flanges being in nested spaced relation and arranged so that the flange on the disc is in abutting contact with said shoulder to provide an annular recess which is closed at one end, a ring of glass in said recess and fused to said flanges, whereby vsaid shell and disk constitute a gas-tight metal envelope, and an electrode assembly in said envelope.

5. An electron tube comprising a metal shell provided with a flange, a metal disk also provided with a flange, said flanges being spaced to form an annular recess, a sealing ring of glass filling said recess and fused to said flanges, whereby said shell and disk constitute a gastight metal envelope, said shell having a circular shoulder engaged by said disk and closing one end of the glass-filled recess, said shoulder also acting as an abutment to hold the disk in predetermined axial relation to the shell, and an electrode assembly in said envelope.

6. An electron tube comprising a sheet metal shell which terminates in a cylindrical flange, a sheet metal disk also terminating in a cylindrical flange, said ilanges being spaced lto provide an annular recess, a ring of glass filling said recess and fused to said flanges, whereby said shell and disk constitute a gas-tight metal envelope, cooperating means on said metal flanges and glass sealing ring for mechanically locking said shell and disk together against axial displacement, said locking means kbeing in addition to the adhesion between the glass and metal parts, and an yelectrode assembly in said envelope.

'7. An electron tube comprising a metal shell provided with a flange, a metal disk also having a flange, said flanges being spaced to form an annular recess, sealing glass insaid recess fused to said flanges, whereby said shell and disk constitute a gas-tight metal envelope, an electrode assembly in said envelope, insulated leadin wires passing through said metal disk and connected to said electrode assembly, a second disk of insulating material carrying contact pins which are connected to said wires, and means for securing said second disk to the metal shell, said second disk abutting against at least one of said flanges to limit its inward axial movement.

8. An electron tube having an envelope formed by a metal shell and a metal disk welded together in a gas-tight joint, insulated lead-in wires passing through said disk, an electrode assembly in said envelope connected to said wires, a metal collar mounted on said shell, said collar being separate from the shell and disk, a base disk of insulating material within said collar, engaging means on said collar and base disk for attaching the latter rigidly to the collar, and contact pins carried by said base disk and connected to said lead-in wires.

9. An electron tube having an envelope formed by a metal shell and a metal disk welded together in a gas-tight joint, insulated lead-in wires passing through said disk, an electrode assembly in said envelope connected to said wires, said shell having an outer annular. shoulder, a metal collar having a rim engaging said shoulder,. a base disk of insulating material arranged within said collar and having peripheral notches, said collar having portions indented into said notches to clamp the base disk to the shell, and contact pins carried by said base disk and connected to the lead-in wires.

10. An electron tube having an envelope containing an electrode assembly, a base disk of insulating material attached to said envelope, said disk having a plurality of holes, a tubular contact pin mounted in each hole, cooperating mechanical means on said disk and pins for positively locking each pin to the disk, said locking means including a hollow bead formed integral on each pin as a radial expansion of its tubular wall, said integral hollow beads abutting against the disk, and means for connecting said pins to the electrode assembly.

1l. An electron tube having an envelope con taining an electrode assembly, a base disk of in sulating material attached to said envelope, said disk having a plurality of holes, a tubular contact pin mounted in each hole, a hollow integral bead on each pin adapted to abut against the disk and limit the axial movement of the pin into its hole, each bead being a hollow radial expansion of the tubular wall of the pin, flanged means on the inner end of each pin engaging the disk, whereby each pin is locked in its hole by said bead and flanged means, and means for connecting said contact pins to said electrode assembly.

comprises supporting parts, placing a glass the shell and disk with circular flanges, supporting the shell and disk in nested relation -so that the tlanges form an annular groove, placing a glass ring in said groove, fusing the glass ring. which substantially nlls the groove, and causing the fused mass ot the figuration which mechanically locks the shell and disk together against axial displacement in addition to the adhesion oi' the glass and metal surfaces, whereby the fused glass ring'unites the l0 metal shell and disk in a strong gas-tight weld.

ADOLPH A. THOMAS. 

